Evidence for lead diagenesis in ancient bones of the Southern Andes David E.B. Fleming a, * , Deborah E. Blom b a Department of Physics, 305 Dunn Building, Mount Allison University, Sackville, New Brunswick, Canada E4L 1E6 b Department of Anthropology, 508 Williams Hall, University of Vermont, Burlington, VT 05405-0068, USA Available online 11 April 2007 Abstract Skeletal samples from pre-Colonial Peru and Bolivia, dating from AD 300 to 1450, were sampled and analyzed for lead content using a non-destructive X-ray fluorescence (XRF) technique. A total of 99 lead measurements were made on bones recovered from three regions of the Southern Andes. Predominantly trabecular bones demonstrated clearly higher lead concentrations than predominantly cortical bones. The magnitudes of lead concentrations and the differences between bony areas that are predominantly cortical and those that are trabecular, indicate diagenesis as the major contributor to observed lead levels. Diagenetic contributions of lead are less sub- stantial in cortical bone. Soil sample analyses confirmed significant quantities of lead in the sediments. Repeated measurements of a tibia and femur from a single individual suggest that the cortical shafts of these bones have similar susceptibilities to lead diagenesis. This is significant for designing alternative sampling strategies in areas where preservation is poor and a specific bone may not be present in all individuals. The XRF system used in this study demonstrates an improved precision of measurement compared with previously reported applications. Ó 2007 Elsevier B.V. All rights reserved. PACS: 78.70.En Keywords: Diagenesis; Bone lead; X-ray fluorescence 1. Introduction Lead toxicity is a major issue in environmental health [1]. Lead has been drawn from the Earth and used by humans for at least 5000 years. In the New World, production of lead has been a relatively more recent activity. Unlike earlier pop- ulations, contemporary humans throughout the world are exposed to significant quantities of lead through multiple environmental pathways. The current ubiquity of lead ren- ders measurement of a ‘‘natural’’ or uncontaminated body concentration impossible in living humans. An area of inter- est is the detection of skeletal lead concentrations in ancient, relatively uncontaminated, human populations [2]. More than 90% of an adult’s lead body burden is contained in bone [3]. Lead concentration in bone may be sampled using X-ray fluorescence (XRF), a technique based on the interaction of radiation with atoms of lead. Since lead is accumulated in the skeleton over a lifetime, past exposure in living subjects can be assessed in a non- invasive fashion by measuring the concentration of lead in bone using XRF [4,5]. A complicating factor making ancient population trace element analysis difficult is dia- genesis, the process by which quantities of a material are exchanged between buried skeletal remains and the sur- rounding soil matrix [6]. The skeletal materials for the current study were system- atically sampled from archaeological collections in Peru and Bolivia. This collection of South Andean bones includes remains from varied geographical terrain, ranging from desert to lakeside conditions. A wide variety of skel- etal elements are represented in the sample. The main objective of this study is to investigate the influence of dia- genesis on lead levels in ancient human bones. 0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2007.04.038 * Corresponding author. Tel.: +1 506 364 2584; fax: +1 506 364 2583. E-mail address: dfleming@mta.ca (D.E.B. Fleming). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 263 (2007) 41–45 NIM B Beam Interactions with Materials & Atoms